1. Field of the Invention
The invention relates to a belt grinding machine having a grinding belt continuously guided about deflection rollers, a pressure shoe for pressing the grinding belt against a workpiece via a contact pressure apparatus, and a contact pressure control whereby a contact pressure force can be set.
2. Description of Related Art
One such belt grinding machine is disclosed, for example, in EP 0 155 380 B1. That belt grinding machine has a segmented pressure beam having a large number of pressure shoes arranged side by side. Each pressure shoe can be controlled to be active or inactive through a detection device that detects the contour of the workpiece, so that only the pressure shoes that are actually needed for the workpiece are set into an active grinding position as the workpiece is conveyed through below the pressure beam by a conveyor device. The setting of the contact pressure force of the activated pressure shoes functions to press those pressure shoes, which have only a small area of contact with a marginal piece of the workpiece, against the workpiece with a reduced contact pressure force to prevent an undesirable rounded grinding of the edges of the workpiece. In this arrangement, the contact pressure force is preferably controlled by a solenoid, whose contact pressure force depends on the electrical power flowing through its coil windings. Other contact pressure devices, for example hydraulic or pneumatic pressure devices, may also be used.
The operation of this known device is as follows: the contour of the workpiece is detected; a contact pressure force is preset by the contact pressure control for the central region of the workpiece; and, in the case of solenoid actuation, the contact pressure control produces a predetermined current through the solenoid of the pressure shoe. A similar principle would apply if pneumatic or hydraulic drives were employed. Despite the sophistication of existing belt grinding machines, there is still room for improvement.